1. Field of the Invention
The present invention relates to an energy converter for a safety belt.
2. Description of the Related Art
Energy converters are known from the DE-OS 23 44 878 wherein the deformation member includes a bushing which embraces a screw bolt at a spacing and which is pushed by a nut, axially displaceable upon the screw bolt, onto a cone which constitutes a component of the screw bolt. The nut is disposed inside a sleeve and is connected with same so as to be capable of transmitting a torque. The belt band or strip of the safety belt is attached to the circumference of the sleeve. The screw bolt is non-rotatably supported by its polyhedral head in the cheek of a U-shaped belt fitting. An exposed threaded segment of the screw bolt penetrates through a parallel cheek of the belt fitting.
A drawback of this type of construction is that the energy conversion cannot be performed on a uniformly high level. Peak loads of the user of the belt are unavoidable. The reasons for this result from the fact that the small area contact of the nut is displaceable upon the screw bolt with only one end segment of the sleeve, and the threaded connection between the nut and the screw bolt, as well as the bushing-like deformation member, is displaceable by the nut in longitudinal direction of the screw bolt which member must be pushed over the cone on the threaded bolt.
Another drawback is that several unrolling revolutions of the belt band, from the sleeve, are necessary for an efficient energy conversion, since with the usual thread pitches, such as they are provided on the screw bolt, there occurs a displacement of the nut across too short a path, in order to convert energy in a defined and reproducible manner. An extension of the belt band, acceptable from the security technology point of view, however, would only at the most, permit two revolutions of the sleeve. If one were to use a thread with an appropriate pitch, it would no longer be procured as a standard part. The advantage connected therewith would then be eliminated.
In addition, there results such an unfavorable force parallelogram at the screw thread flanks, between the screw bolt and the nut, that the turning of the sleeve is only possible when using a very soft deformation or resilient member. Any change of friction in the thread thus immediately changes the load-strain characteristic at the belt band. With mass production, there results therefrom a special drawback, since a constant effectiveness can only be assured with a great expenditure of mechanical apparatus.